Rename TU names to not conflict with libc++.

In order to easily merge libc++ and libc++abi static archives it's important
that none of the source files share the same name.
(See http://stackoverflow.com/questions/3821916/how-to-merge-two-ar-static-libraries-into-one)

This patch renames source files which share a name with libc++ sources.

llvm-svn: 287327